Brain Stimulation for Torsion Dystonia

Connecting the dots - A systematic review on coherence analysis in dystonia

BACKGROUND

Increased 4-12 Hz oscillatory activity in the cortico-basal ganglia-thalamo-cortical (CBGTC) loop is reported in dystonia. Coherence analysis is a measure of linear coupling between two signals, revealing oscillatory activity drives that are common across motor units. By performing coherence analysis, activity of the CBGTC-loop can be measured with modalities like local field potentials (LFPs), electromyography (EMG), and electro-encephalography (EEG). The aim of this study is to perform a systematic review on the use of coherence analysis for clinical assessment and treatment of dystonia.

METHODS

A systematic review was performed on a search in Embase and PubMed on June 28th, 2023. All studies incorporating coherence analysis and an adult dystonia cohort were included. Three authors evaluated the eligibility of the articles. Quality was assessed using the QUADAS-2 checklist.

RESULTS

A total of 41 articles were included, with data of 395 adult dystonia patients. In the selected records, six different types of coherence were investigated: corticocortical, corticopallidal, corticomuscular, pallidopallidal, pallidomuscular, and intermuscular coherence. Various types of 4-12 coherence were found to be increased in all dystonia subtypes.

CONCLUSION

There is increased 4-12 Hz coherence found between the cortex, basal ganglia, and affected muscles in all dystonia subtypes. However, the relationship between 4-12 Hz coherence and the dystonic clinical state has not been established. DBS treatment leads to a reduction of 4-12 Hz coherence. In combination with the results of this review, the 4-12 Hz frequency band can be used as a promising phenomenon for the development of a biomarker.

The role of genetics in the treatment of dystonia with deep brain stimulation: Systematic review and Meta-analysis

BACKGROUND

Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions that lead to involuntary postures or repetitive movements. Genetic mutations are being increasingly recognized as a cause of dystonia. Deep brain stimulation (DBS) is one of the limited treatment options available. However, there are varying reports on its efficacy in genetic dystonias. This systematic review of the characteristics of genetic dystonias treated with DBS and their outcomes aims to aid in the evaluation of eligibility for such treatment.

METHODS

We performed a PUBMED search of all papers related to genetic dystonias and DBS up until April 2022. In addition to performing a systematic review, we also performed a meta-analysis to assess the role of the mutation on DBS response. We included cases that had a confirmed genetic mutation and DBS along with pre-and post-operative BFMDRS.

RESULTS

Ninety-one reports met our inclusion criteria and from them, 235 cases were analyzed. Based on our analysis DYT-TOR1A dystonia had the best evidence for DBS response and Rapid-Onset Dystonia Parkinsonism was among the least responsive to DBS.

CONCLUSION

While our report supports the role of genetics in DBS selection and response, it is limited by the rarity of the individual genetic conditions, the reliance on case reports and case series, and the limited ability to obtain genetic testing on a large scale in real-time as opposed to retrospectively as in many cases.

Long-Term Outcome of Subthalamic Deep Brain Stimulation for Generalized Isolated Dystonia

OBJECTIVES

Few studies have focused on subthalamic nucleus deep brain stimulation for refractory isolated dystonia, and the long-term outcomes are unclear. In this study, we evaluated the efficacy of subthalamic stimulation for generalized isolated dystonia for more than five years and explored the factors predicting clinical outcomes.

MATERIALS AND METHODS

A total of 16 patients with generalized isolated dystonia underwent a two-phase procedure for stimulation system implantation. After implanting the leads, we performed a test stimulation and observed the stimulation response. The severity of dystonia was assessed using a blinded rating of the Burke-Fahn-Marsden Dystonia Rating Scale based on videos recorded at scheduled times.

RESULTS

The mean follow-up time was 7.4 ± 2.2 years (5-12.5 years). The severity of dystonia improved significantly one year after surgery. The movement score decreased from 49.3 (40.9) points at baseline to 26.5 (43.5) points (-44.6%) at six months, 12.0 (22.5) points (-66.8%) at one year, 11.25 (17.6) points (-72.7%) at three years, and 12.5 (21.0) points (-72.6%) at the last follow-up. The improvement in motor symptoms resulted in a corresponding improvement in activities of daily living. Greater long-term outcomes were correlated with early stimulation responses, lower baseline movement scores, and female sex. When analyzed comprehensively, only the baseline movement score had meaningful predictive value for the outcome.

CONCLUSIONS

Our results indicate that subthalamic stimulation is effective and durable in treating generalized isolated dystonia. The subthalamic nucleus may be an alternative target for the treatment of refractory dystonia. Patients with less severe motor symptoms may benefit more from this treatment.

A low dimensional embedding of brain dynamics enhances diagnostic accuracy and behavioral prediction in stroke

Large-scale brain networks reveal structural connections as well as functional synchronization between distinct regions of the brain. The latter, referred to as functional connectivity (FC), can be derived from neuroimaging techniques such as functional magnetic resonance imaging (fMRI). FC studies have shown that brain networks are severely disrupted by stroke. However, since FC data are usually large and high-dimensional, extracting clinically useful information from this vast amount of data is still a great challenge, and our understanding of the functional consequences of stroke remains limited. Here, we propose a dimensionality reduction approach to simplify the analysis of this complex neural data. By using autoencoders, we find a low-dimensional representation encoding the fMRI data which preserves the typical FC anomalies known to be present in stroke patients. By employing the latent representations emerging from the autoencoders, we enhanced patients' diagnostics and severity classification. Furthermore, we showed how low-dimensional representation increased the accuracy of recovery prediction.

Bilateral globus pallidus internus (GPi) deep brain stimulation for cervical dystonia: Effects on motor and non-motor symptoms within 5 years follow

BACKGROUND

Cervical Dystonia ("CD") is a movement disorder characterised by sustained muscle contractions in the neck, causing involuntary posturing. Deep brain stimulation ("DBS") of the globus pallidal internus (GPi) is advanced treatment for pharmaco-refractory patients. As CD is a rare disease, cohort studies are often limited to patients of heterogenous disease profile, small sample size or short follow-up. This study firstly aimed to measure the efficacy of GPi-DBS on motor and non-motor symptoms of CD. A secondary aim was to evaluate if clinical factors - such as age, disease duration and baseline disease severity - influence variability of motor outcomes.

METHODS

37 idiopathic CD patients were recruited from movement disorders clinics at The Walton NHS Foundation Trust, Liverpool, UK. Patients were assessed pre-operatively, and 1 year, 3 years and 5 years post-operatively with the following clinical scales: Toronto Western Spasmodic Torticollis Rating Scale ("TWSTRS"), Hospital Anxiety and Depression Scale and EuroQuol-5D.

RESULTS

GPI-DBS significantly improved overall TWSTRS scores by 57% from baseline to 5Y FU (p < 0.001). It also significantly improved TWSTRS severity, disability, and pain sub-scores by 72%, 59% and 46% respectively. We did not find a significant improvement in mood or quality of life scores at 5 years. Similarly, clinical factors at baseline did not correlate with variability in motor outcome.

CONCLUSION

We concluded that GPi-DBS is an effective treatment for motor symptoms and pain in CD. There was limited effect on mood and QoL, and no clinical predictive factors of outcome were identified.

DYT-TOR1A dystonia: an update on pathogenesis and treatment

DYT-TOR1A dystonia is a neurological disorder characterized by involuntary muscle contractions and abnormal movements. It is a severe genetic form of dystonia caused by mutations in the TOR1A gene. TorsinA is a member of the AAA + family of adenosine triphosphatases (ATPases) involved in a variety of cellular functions, including protein folding, lipid metabolism, cytoskeletal organization, and nucleocytoskeletal coupling. Almost all patients with TOR1A-related dystonia harbor the same mutation, an in-frame GAG deletion (ΔGAG) in the last of its 5 exons. This recurrent variant results in the deletion of one of two tandem glutamic acid residues (i.e., E302/303) in a protein named torsinA [torsinA(△E)]. Although the mutation is hereditary, not all carriers will develop DYT-TOR1A dystonia, indicating the involvement of other factors in the disease process. The current understanding of the pathophysiology of DYT-TOR1A dystonia involves multiple factors, including abnormal protein folding, signaling between neurons and glial cells, and dysfunction of the protein quality control system. As there are currently no curative treatments for DYT-TOR1A dystonia, progress in research provides insight into its pathogenesis, leading to potential therapeutic and preventative strategies. This review summarizes the latest research advances in the pathogenesis, diagnosis, and treatment of DYT-TOR1A dystonia.

An Argument in Favor of Deep Brain Stimulation for Uncommon Movement Disorders: The Case for N-of-1 Trials in Holmes Tremor

Deep brain stimulation (DBS) is part of state-of-the-art treatment for medically refractory Parkinson’s disease, essential tremor or primary dystonia. However, there are multiple movement disorders that present after a static brain lesion and that are frequently refractory to medical treatment. Using Holmes tremor (HT) as an example, we discuss the effectiveness of currently available treatments and, performing simulations using a Markov Chain approach, propose that DBS with iterative parameter optimization is expected to be more effective than an approach based on sequential trials of pharmacological agents. Since, in DBS studies for HT, the thalamus is a frequently chosen target, using data from previous studies of lesion connectivity mapping in HT, we compared the connectivity of thalamic and non-thalamic targets with a proxy of the HT network, and found a significantly higher connectivity of thalamic DBS targets in HT. The understanding of brain networks provided by analysis of functional connectivity may thus provide an informed framework for proper surgical targeting of individual patients. Based on these findings, we argue that there is an ethical imperative to at least consider surgical options in patients with uncommon movement disorders, while simultaneously providing consistent information regarding the expected effectiveness and risks, even in a scenario of surgical-risk aversion. An approach based on n-of-1 DBS trials may ultimately significantly improve outcomes while informing on optimal therapeutic targets and parameter settings for HT and other disabling and rare movement disorders.

Development and Characterization of Novel Conductive Sensing Fibers for In Vivo Nerve Stimulation

Advancements in electrode technologies to both stimulate and record the central nervous system's electrical activities are enabling significant improvements in both the understanding and treatment of different neurological diseases. However, the current neural recording and stimulating electrodes are metallic, requiring invasive and damaging methods to interface with neural tissue. These electrodes may also degrade, resulting in additional invasive procedures. Furthermore, metal electrodes may cause nerve damage due to their inherent rigidity. This paper demonstrates that novel electrically conductive organic fibers (ECFs) can be used for direct nerve stimulation. The ECFs were prepared using a standard polyester material as the structural base, with a carbon nanotube ink applied to the surface as the electrical conductor. We report on three experiments: the first one to characterize the conductive properties of the ECFs; the second one to investigate the fiber cytotoxic properties in vitro; and the third one to demonstrate the utility of the ECF for direct nerve stimulation in an in vivo rodent model.

Characterization of the direct pathway in Dyt1 ΔGAG heterozygous knock-in mice and dopamine receptor 1-expressing-cell-specific Dyt1 conditional knockout mice

DYT1 dystonia is a movement disorder mainly caused by a trinucleotide deletion (ΔGAG) in DYT1 (TOR1A), coding for torsinA. DYT1 dystonia patients show trends of decreased striatal ligand-binding activities to dopamine receptors 1 (D1R) and 2 (D2R). Dyt1 ΔGAG knock-in (KI) mice, which have the corresponding ΔGAG deletion, similarly exhibit reduced striatal D1R and D2R-binding activities and their expression levels. While the consequences of D2R reduction have been well characterized, relatively little is known about the effect of D1R reduction. Here, locomotor responses to D1R and D2R antagonists were examined in Dyt1 KI mice. Dyt1 KI mice showed significantly less responsiveness to both D1R antagonist SCH 23390 and D2R antagonist raclopride. The electrophysiological recording indicated that Dyt1 KI mice showed a significantly increased paired-pulse ratio of the striatal D1R-expressing medium spiny neurons and altered miniature excitatory postsynaptic currents. To analyze the in vivo torsinA function in the D1R-expressing neurons further, Dyt1 conditional knockout (Dyt1 d1KO) mice in these neurons were generated. Dyt1 d1KO mice had decreased spontaneous locomotor activity and reduced numbers of slips in the beam-walking test. Dyt1 d1KO male mice showed abnormal gait. Dyt1 d1KO mice showed defective striatal D1R maturation. Moreover, the mutant striatal D1R-expressing medium spiny neurons had increased capacitance, decreased sEPSC frequency, and reduced intrinsic excitability. The results suggest that torsinA in the D1R-expressing cells plays an important role in the electrophysiological function and motor performance. Medical interventions to the direct pathway may affect the onset and symptoms of this disorder.

Deep Brain Stimulation for Tremor and Dystonia

Deep brain stimulation (DBS) is the most commonly used surgical treatment for drug-refractory movement disorders such as tremor and dystonia. Appropriate patient selection along with target selection is important to ensure optimal outcome without complications. This review summarizes the recent literature regarding the mechanism of action, indications, outcome, and complications of DBS in tremor and dystonia. A comparison with other modalities of surgical interventions is discussed along with a note of the recent advances in technology. Future research needs to be directed to understand the underlying etiopathogenesis of the disease and the way in which DBS modulates the intracranial abnormal networks.

Globus Pallidus Internus Deep Brain Stimulation for Dystonic Opisthotonus in Adult-Onset Dystonia: A Personalized Approach

Introduction

Dystonic opisthotonus is defined as a backward arching of the neck and trunk, which ranges in severity from mild backward jerks to life-threatening prolonged severe muscular spasms. It can be associated with generalized dystonic syndromes or, rarely, present as a form of axial truncal dystonia. The etiologies vary from idiopathic, genetic, tardive, hereditary-degenerative, or associated with parkinsonism. We report clinical cases of dystonic opisthotonus associated with adult-onset dystonic syndromes, that benefitted from globus pallidus internus (GPi) deep brain stimulation (DBS).

Methods

Clinical data from patients with dystonic syndromes who underwent comprehensive medical review, multidisciplinary assessment, and tailored medical and neurosurgical managements were prospectively analyzed. Quantification of dystonia severity pre- and postoperatively was performed using the Burke-Fahn-Marsden Dystonia Rating Scale and quantification of overall pain severity was performed using the Visual Analog Scale.

Results

Three male patients, with age of onset of the dystonic symptoms ranging from 32 to 51 years old, were included. Tardive dystonia, adult-onset dystonia-parkinsonism and adult-onset idiopathic axial dystonia were the etiologies identified. Clinical investigation and management were tailored according to the complexity of the individual presentations. Although they shared common clinical features of adult-onset dystonia, disabling dystonic opisthotonus, refractory to medical management, was the main indication for GPi-DBS in all patients presented. The severity of axial dystonia ranged from disturbance of daily function to life-threatening truncal distortion. All three patients underwent bilateral GPi DBS at a mean age of 52 years (range 48–55 years), after mean duration of symptoms prior to DBS of 10.7 years (range 4–16 years). All patients showed a rapid and sustained clinical improvement of their symptoms, notably of the dystonic opisthotonos, at postoperative follow-up ranging from 20 to 175 months. In some, the ability to resume activities of daily living and reintegration into the society was remarkable.

Conclusion

Adult-onset dystonic syndromes predominantly presenting with dystonic opisthotonus are relatively rare. The specific nature of dystonic opisthotonus remains a treatment challenge, and thorough investigation of this highly disabling condition with varying etiologies is often necessary. Although patients may be refractory to medical management and botulinum toxin injection, Globus pallidus stimulation timed and tailored provided symptomatic control in this cohort and may be considered in other carefully selected cases.

Targeting accuracy of robot-assisted deep brain stimulation surgery in childhood-onset dystonia: a single-center prospective cohort analysis of 45 consecutive cases

OBJECTIVE

Deep brain stimulation (DBS) is an established treatment for pediatric dystonia. The accuracy of electrode implantation is multifactorial and remains a challenge in this age group, mainly due to smaller anatomical targets in very young patients compared to adults, and also due to anatomical abnormalities frequently associated with some etiologies of dystonia. Data on the accuracy of robot-assisted DBS surgery in children are limited. The aim of the current paper was to assess the accuracy of robot-assisted implantation of DBS leads in a series of patients with childhood-onset dystonia.

METHODS

Forty-five children with dystonia undergoing implantation of DBS leads under general anesthesia between 2017 and 2019 were included. Robot-assisted stereotactic implantation of the DBS leads was performed. The final position of the electrodes was verified with an intraoperative 3D scanner (O-arm). Coordinates of the planned electrode target and actual electrode position were obtained and compared, looking at the radial error, depth error, absolute error, and directional error, as well as the euclidean distance. Functional assessment data prospectively collected by a multidisciplinary pediatric complex motor disorders team were analyzed with regard to motor skills, individualized goal achievement, and patients' and caregivers' expectations.

RESULTS

A total of 90 DBS electrodes were implanted and 48.5% of the patients were female. The mean age was 11.0 ± 0.6 years (range 3-18 years). All patients received bilateral DBS electrodes into the globus pallidus internus. The median absolute errors in x-, y-, and z-axes were 0.85 mm (range 0.00-3.25 mm), 0.75 mm (range 0.05-2.45 mm), and 0.75 mm (range 0.00-3.50 mm), respectively. The median euclidean distance from the target to the actual electrode position was 1.69 ± 0.92 mm, and the median radial error was 1.21 ± 0.79. The robot-assisted technique was easily integrated into the authors' surgical practice, improving accuracy and efficiency, and reducing surgical time significantly along the learning curve. No major perioperative complications occurred.

CONCLUSIONS

Robot-assisted stereotactic implantation of DBS electrodes in the pediatric age group is a safe and accurate surgical method. Greater accuracy was present in this cohort in comparison to previous studies in which conventional stereotactic frame-based techniques were used. Robotic DBS surgery and neuroradiological advances may result in further improvement in surgical targeting and, consequently, in better clinical outcome in the pediatric population.

Abnormal cerebellar function and tremor in a mouse model for non-manifesting partially penetrant dystonia type 6

KEY POINTS

Loss-of-function mutations in the Thap1 gene cause partially penetrant dystonia type 6 (DYT6). Some non-manifesting DYT6 mutation carriers have tremor and abnormal cerebello-thalamo-cortical signalling. We show that Thap1 heterozygote mice have action tremor, a reduction in cerebellar neuron number, and abnormal electrophysiological signals in the remaining neurons. These results underscore the importance of Thap1 levels for cerebellar function. These results uncover how cerebellar abnormalities contribute to different dystonia-associated motor symptoms.

ABSTRACT

Loss-of-function mutations in the Thanatos-associated domain-containing apoptosis-associated protein 1 (THAP1) gene cause partially penetrant autosomal dominant dystonia type 6 (DYT6). However, the neural abnormalities that promote the resultant motor dysfunctions remain elusive. Studies in humans show that some non-manifesting DYT6 carriers have altered cerebello-thalamo-cortical function with subtle but reproducible tremor. Here, we uncover that Thap1 heterozygote mice have action tremor that rises above normal baseline values even though they do not exhibit overt dystonia-like twisting behaviour. At the neural circuit level, we show using in vivo recordings in awake Thap1+/- mice that Purkinje cells have abnormal firing patterns and that cerebellar nuclei neurons, which connect the cerebellum to the thalamus, fire at a lower frequency. Although the Thap1+/- mice have fewer Purkinje cells and cerebellar nuclei neurons, the number of long-range excitatory outflow projection neurons is unaltered. The preservation of interregional connectivity suggests that abnormal neural function rather than neuron loss instigates the network dysfunction and the tremor in Thap1+/- mice. Accordingly, we report an inverse correlation between the average firing rate of cerebellar nuclei neurons and tremor power. Our data show that cerebellar circuitry is vulnerable to Thap1 mutations and that cerebellar dysfunction may be a primary cause of tremor in non-manifesting DYT6 carriers and a trigger for the abnormal postures in manifesting patients.

Arching deep brain stimulation in dystonia types

Although medical treatment including botulinum toxic injection is the first-line treatment for dystonia, response is insufficient in many patients. In these patients, deep brain stimulation (DBS) can provide significant clinical improvement. Mounting evidence indicates that DBS is an effective and safe treatment for dystonia, especially for idiopathic and inherited isolated generalized/segmental dystonia, including DYT-TOR1A. Other inherited dystonia and acquired dystonia also respond to DBS to varying degrees. For Meige syndrome (craniofacial dystonia), other focal dystonia, and some rare inherited dystonia, further evidences are still needed to evaluate the role of DBS. Because short disease duration at DBS surgery and absence of fixed musculoskeletal deformity are associated with better outcome, DBS should be considered as early as possible when indicated after careful evaluation including genetic work-up. This review will focus on the factors to be considered in DBS for patients with dystonia and the outcome of DBS in the different types of dystonia.

The abnormal firing of Purkinje cells in the knockin mouse model of DYT1 dystonia

DYT1 dystonia is an inherited movement disorder caused by a heterozygous trinucleotide (GAG) deletion in DYT1/TOR1A, coding for torsinA. Growing evidence suggests that the cerebellum plays a role in the pathogenesis of dystonia. Brain imaging of both DYT1 dystonia patients and animal models show abnormal activity in the cerebellum. The cerebellum-specific knockdown of torsinA in adult mice leads to dystonia-like behavior. Dyt1 ΔGAG heterozygous knock-in mouse model exhibits impaired corticostriatal long-term depression, abnormal muscle co-contraction, and motor deficits. We and others previously reported altered dendritic structures in Purkinje cells in Dyt1 knock-in mouse models. However, whether there are any electrophysiological alterations of the Purkinje cells in Dyt1 knock-in mice is not known. We used the patch-clamp recording in brain slices and in acutely dissociated Purkinje cells to identify specific alterations of Purkinje cells firing. We found abnormal firing of non-tonic type of Purkinje cells in the Dyt1 knock-in mice. Furthermore, the large-conductance calcium-activated potassium (BK) current and the BK channel protein levels were significantly increased in the Dyt1 knock-in mice. Our results support a role of the cerebellum in the pathogenesis of DYT1 dystonia. Manipulating the Purkinje cell firing and cerebellar output may show great promise for treating DYT1 dystonia.

Deep Brain Stimulation of the Internal Pallidum in Lesch-Nyhan Syndrome: Clinical Outcomes and Connectivity Analysis

BACKGROUND

Lesch-Nyhan syndrome (LNS) is a rare genetic disorder characterized by a deficiency of hypoxanthine-guanine phosphoribosyltransferase enzyme. It manifests during infancy with compulsive self-mutilation behavior associated with disabling generalized dystonia and dyskinesia. Clinical management of these patients poses an enormous challenge for medical teams and carers.

OBJECTIVES

We report our experience with bilateral deep brain stimulation (DBS) of the globus pallidus internus (GPi) in the management of this complex disorder.

MATERIALS AND METHODS

Preoperative and postoperative functional assessment data prospectively collected by a multidisciplinary pediatric complex motor disorders team, including imaging, neuropsychology, and neurophysiology evaluations were analyzed with regards to motor and behavioral control, goal achievement, and patient and caregivers' expectations.

RESULTS

Four male patients (mean age 13 years) underwent DBS implantation between 2011 and 2018. Three patients received double bilateral DBS electrodes within the posteroventral GPi and the anteromedial GPi, whereas one patient had bilateral electrodes placed in the posteroventral GPi only. Median follow-up was 47.5 months (range 22-98 months). Functional improvement was observed in all patients and discussed in relation to previous reports. Analysis of structural connectivity revealed significant correlation between the involvement of specific cortical regions and clinical outcome.

CONCLUSION

Combined bilateral stimulation of the anteromedial and posteroventral GPi may be considered as an option for managing refractory dystonia and self-harm behavior in LNS patients. A multidisciplinary team-based approach is essential for patient selection and management, to support children and families, to achieve functional improvement and alleviate the overall disease burden for patients and caregivers.

Characteristics of globus pallidus internus local field potentials in generalized dystonia patients with TWNK mutation

OBJECTIVE

We focused on a rare gene mutation causing dystonia in two siblings who received globus pallidus internus deep brain stimulation (GPi-DBS). The aim was to characterize the relationship between neuronal activity patterns and clinical syndromes.

METHODS

Whole exome sequencing was applied to identify the TWNK (previous symbol C10orf2) mutation; Two siblings with TWNK mutation presented as generalized dystonia with rigidity and bradykinesia; four other sporadic generalized dystonia patients underwent GPi-DBS and local field potentials (LFPs) were recorded. Oscillatory activities were illustrated with power spectra and temporal dynamics measured by the Lempel-Ziv complexity (LZC).

RESULTS

Normalized power spectra of GPi LFPs differed between patients with TWNK mutation and dystonia over the low beta bands. Patients with TWNK mutation had higher low beta power (15-27 Hz, unpaired t-test, corrected P < 0.0022) and lower LZC (15-27 Hz, unpaired t-test, P < 0.01) than other patients with generalized dystonia. On the other hand, the TWNK mutation patients showed decreased low frequency and beta oscillation in the GPi after DBS, as well as improved movement performance.

CONCLUSION

The LFPs were different in TWNK mutation dystonia siblings than other patients with generalized dystonia, which indicate the abnormal LFPs were related to symptoms rather than specific disease. In addition, the inhibited effect on oscillations also provided a potential evidence for DBS treatment on rare movement disorders.

SIGNIFICANCE

This study could potentially aid in the future development of adaptive DBS via rare disease LFPs comparison.

Differential response to pallidal deep brain stimulation among monogenic dystonias: systematic review and meta-analysis

OBJECTIVE

Genetic subtypes of dystonia may respond differentially to deep brain stimulation of the globus pallidus pars interna (GPi DBS). We sought to compare GPi DBS outcomes among the most common monogenic dystonias.

METHODS

This systematic review and meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses and Meta-analysis of Observational Studies in Epidemiology guidelines. We searched PubMed for studies on genetically confirmed monogenic dystonia treated with GPi DBS documenting pre-surgical and post-surgical assessments using the Burke-Fahn-Marsden Dystonia Rating Scale Motor Score (BFMMS) and Burke-Fahn-Marsden Disability Score (BFMDS). We performed (i) meta-analysis for each gene mutation; (ii) weighted ordinary linear regression analyses to compare BFMMS and BFMDS outcomes between DYT-TOR1A and other monogenic dystonias, adjusting for age and disease duration and (iii) weighted linear regression analysis to estimate the effect of age, sex and disease duration on GPi DBS outcomes. Results were summarised with mean change and 95% CI.

RESULTS

DYT-TOR1A (68%, 38.4 points; p<0.001), DYT-THAP1 (37% 14.5 points; p<0.001) and NBIA/DYT-PANK2 (27%, 21.4 points; p<0.001) improved in BFMMS; only DYT-TOR1A improved in BFMDS (69%, 9.7 points; p<0.001). Improvement in DYT-TOR1A was significantly greater than in DYT-THAP1 (BFMMS -31%), NBIA/DYT-PANK2 (BFMMS -35%; BFMDS -53%) and CHOR/DYT-ADCY5 (BFMMS -36%; BFMDS -42%). Worse motor outcomes were associated with longer dystonia duration and older age at dystonia onset in DYT-TOR1A, longer dystonia duration in DYT/PARK-TAF1 and younger age at dystonia onset in DYT-SGCE.

CONCLUSIONS

GPi DBS outcomes vary across monogenic dystonias. These data serve to inform patient selection and prognostic counselling.

Advances in the pathophysiology of adult-onset focal dystonias: recent neurophysiological and neuroimaging evidence

Focal dystonia is a movement disorder characterized by involuntary muscle contractions that determine abnormal postures. The traditional hypothesis that the pathophysiology of focal dystonia entails a single structural dysfunction (i.e. basal ganglia) has recently come under scrutiny. The proposed network disorder model implies that focal dystonias arise from aberrant communication between various brain areas. Based on findings from animal studies, the role of the cerebellum has attracted increased interest in the last few years. Moreover, it has been increasingly reported that focal dystonias also include nonmotor disturbances, including sensory processing abnormalities, which have begun to attract attention. Current evidence from neurophysiological and neuroimaging investigations suggests that cerebellar involvement in the network and mechanisms underlying sensory abnormalities may have a role in determining the clinical heterogeneity of focal dystonias.

Pallidal Deep Brain Stimulation in DYT6 Dystonia: Clinical Outcome and Predictive Factors for Motor Improvement

Pallidal deep brain stimulation is an established treatment in dystonia. Available data on the effect in DYT-THAP1 dystonia (also known as DYT6 dystonia) are scarce and long-term follow-up studies are lacking. In this retrospective, multicenter follow-up case series of medical records of such patients, the clinical outcome of pallidal deep brain stimulation in DYT-THAP1 dystonia, was evaluated. The Burke Fahn Marsden Dystonia Rating Scale served as an outcome measure. Nine females and 5 males were enrolled, with a median follow-up of 4 years and 10 months after implant. All benefited from surgery: dystonia severity was reduced by a median of 58% (IQR 31-62, p = 0.001) at last follow-up, as assessed by the Burke Fahn Marsden movement subscale. In the majority of individuals, there was no improvement of speech or swallowing, and overall, the effect was greater in the trunk and limbs as compared to the cranio-cervical and orolaryngeal regions. No correlation was found between disease duration before surgery, age at surgery, or preoperative disease burden and the outcome of deep brain stimulation. Device- and therapy-related side-effects were few. Accordingly, pallidal deep brain stimulation should be considered in clinically impairing and pharmaco-resistant DYT-THAP1 dystonia. The method is safe and effective, both short- and long-term.

Quality of life outcomes after deep brain stimulation in dystonia: A systematic review

Dystonia is an incurable movement disorder which can cause not only physical but also mental problems, leading to impaired health-related quality of life (HRQoL). For patients with dystonia refractory to medical treatment, deep brain stimulation (DBS) is a well-established surgical treatment. The objective of this systematic review is to provide a better understanding of HRQoL outcomes after DBS for dystonia. A search of the literature was conducted using Medline (PubMed), Embase, and Cochrane Library databases in May 2019. HRQoL outcomes after DBS along with motor outcomes were reported in a total of 36 articles involving 610 patients: 21 articles on inherited or idiopathic isolated dystonia, 5 on tardive dystonia, 3 on cerebral palsy, 2 on myoclonus-dystonia, 1 on X-linked dystonia-parkinsonism, and 3 on mixed cohorts of different dystonia subtypes. DBS improved motor symptoms in various subtypes of dystonia. Most studies on patients with inherited or idiopathic isolated dystonia showed significant improvement in physical QoL, whereas gains in mental QoL were less robust and likely related to the complexity of associated neuropsychiatric problems. HRQoL outcomes beyond 5 years remain scarce. Although the studies on patients with other subtypes of dystonia also demonstrated improvement in HRQoL after DBS, the interpretation is difficult because of a limited number of articles with small cohorts. Most articles employed generic measures (e.g. Short Form Health Survey-36) and this highlights the critical need to develop and to utilize sensitive and disease-specific HRQoL measures. Finally, long-term HRQoL outcomes and predictors of HRQoL should also be clarified.

Selective Cervical Denervation for Cervical Dystonia: Modification of the Bertrand Procedure

BACKGROUND

Cervical dystonia, commonly referred to as spasmodic torticollis, is a neurological disorder characterized by aberrant, involuntary contraction of the muscles of the neck and shoulders. One surgical option that can be considered is selective cervical denervation.

OBJECTIVE

To report our modification of the Bertrand procedure for selective cervical denervation.

METHODS

Our modification of the Bertrand procedure for selective cervical denervation is reported with intraoperative photographs and schematic depictions of the operative steps.

RESULTS

We report our modification of the Bertrand procedure for selective cervical denervation, which consists of a combination of C2-6 denervation, myectomy of the splenius capitis and/or semispinalis capitis, myotomy of the levator scapulae when indicated, and myotomy and selection denervation of the sternocleidomastoid. The combination of techniques utilized depends on the subtype and severity of cervical dystonia.

CONCLUSION

Our modification of the original Bertrand procedure for selective cervical denervation represents an alternative surgical strategy for the treatment of cervical dystonia, with the potential advantages and disadvantages discussed.

Update on current and emerging therapies for dystonia

Treatment strategies for dystonia depend on the focal, segmental or generalized distribution of symptoms. Chemodenervation with botulinum toxin remains the treatment of choice for focal- or select-body regions in generalized and segmental dystonia. A potentially longer acting formulation of botulinum toxin is being investigated besides the currently available formulations. Electromyography increases toxin injection accuracy and may reduce injection number, frequency, side effects and costs by identifying dystonic muscle activity. Oral anticholinergics, baclofen and clonazepam are used off-label, but novel drugs in development include sodium oxybate, zonisamide and perampanel. Characterizing dystonia as a sensorimotor circuit disorder has prompted the use of noninvasive neuromodulation procedures. These techniques need further study but simultaneous rehabilitation techniques appear to also improve outcomes. Pallidal deep-brain stimulation is beneficial for medication-refractory primary generalized and possibly focal dystonia such as cervical dystonia. Certain genetic conditions are amenable to specific therapies and future gene-targeted therapies could benefit selected dystonia patients.

Current therapies and therapeutic decision making for childhood-onset movement disorders

Movement disorders differ in children to adults. First, neurodevelopmental movement disorders such as tics and stereotypies are more prevalent than parkinsonism, and second, there is a genomic revolution which is now explaining many early-onset dystonic syndromes. We outline an approach to children with movement disorders starting with defining the movement phenomenology, determining the level of functional impairment due to abnormal movements, and screening for comorbid psychiatric conditions and cognitive impairments which often contribute more to disability than the movements themselves. The rapid improvement in our understanding of the etiology of movement disorders has resulted in an increasing focus on precision medicine, targeting treatable conditions and defining modifiable disease processes. We profile some of the key disease-modifying therapies in metabolic, neurotransmitter, inflammatory, and autoimmune conditions and the increasing focus on gene or cellular therapies. When no disease-modifying therapies are possible, symptomatic therapies are often all that is available. These classically target dopaminergic, cholinergic, alpha-adrenergic, or GABAergic neurochemistry. Increasing interest in neuromodulation has highlighted that some clinical syndromes respond better to DBS, and further highlights the importance of "disease-specific" therapies with a future focus on individualized therapies according to the genomic findings or disease pathways that are disrupted. We summarize some pragmatic applications of symptomatic therapies, neuromodulation techniques, and some rehabilitative interventions and provide a contemporary overview of treatment in childhood-onset movement disorders. © 2019 International Parkinson and Movement Disorder Society.

Deep Brain Stimulation Versus Peripheral Denervation for Cervical Dystonia: A Systematic Review and Meta-Analysis

BACKGROUND

Cervical dystonia is a disabling medical condition that drastically decreases quality of life. Surgical treatment consists of peripheral nerve denervation procedures with or without myectomies or deep brain stimulation (DBS). The current objective was to compare the efficacy of peripheral denervation versus DBS in improving the severity of cervical dystonia through a systematic review and meta-analysis.

METHODS

A search of PubMed, MEDLINE, EMBASE, and Web of Science electronic databases was conducted in accordance with PRISMA guidelines. Preoperative and postoperative Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) total scores were used to generate standardized mean differences and 95% confidence intervals (CIs), which were combined in a random-effects model. Both mean percentage and absolute reduction in TWSTRS scores were calculated. Absolute reduction was used for forest plots.

RESULTS

Eighteen studies met the inclusion criteria, comprising 870 patients with 180 (21%) undergoing DBS and 690 (79%) undergoing peripheral denervation procedures. The mean follow-up time was 31.5 months (range, 12-38 months). In assessing the efficacy of each intervention, forest plots revealed significant absolute reduction in total postoperative TWSTRS scores for both peripheral denervation (standardized mean difference 1.54; 95% CI 1.42-1.66) and DBS (standardized mean difference 2.07; 95% CI 1.43-2.71). On subgroup analysis, DBS therapy was significantly associated with improvement in postoperative TWSTRS severity (standardized mean difference 2.08; 95% CI 1.66-2.50) and disability (standardized mean difference 2.12; 95% CI 1.57-2.68) but not pain (standardized mean difference 1.18; 95% CI 0.80-1.55).

CONCLUSIONS

Both peripheral denervation and DBS are associated with a significant reduction in absolute TWSTRS total score, with no significant difference in the magnitude of reduction observed between the 2 treatments. Further comparative data are needed to better evaluate the long-term results of both interventions.

Individualized tractography-based parcellation of the globus pallidus pars interna using 7T MRI in movement disorder patients prior to DBS surgery

The success of deep brain stimulation (DBS) surgeries for the treatment of movement disorders relies on the accurate placement of an electrode within the motor portion of subcortical brain targets. However, the high number of electrodes requiring relocation indicates that today's methods do not ensure sufficient accuracy for all patients. Here, with the goal of aiding DBS targeting, we use 7 Tesla (T) MRI data to identify the functional territories and parcellate the globus pallidus pars interna (GPi) into motor, associative and limbic regions in individual subjects. 7 T MRI scans were performed in seventeen patients (prior to DBS surgery) and one healthy control. Tractography-based parcellation of each patient's GPi was performed. The cortex was divided into four masks representing motor, limbic, associative and "other" regions. Given that no direct connections between the GPi and the cortex have been shown to exist, the parcellation was carried out in two steps: 1) The thalamus was parcellated based on the cortical targets, 2) The GPi was parcellated using the thalamus parcels derived from step 1. Reproducibility, via repeated scans of a healthy subject, and validity of the findings, using different anatomical pathways for parcellation, were assessed. Lastly, post-operative imaging data was used to validate and determine the clinical relevance of the parcellation. The organization of the functional territories of the GPi observed in our individual patient population agrees with that previously reported in the literature: the motor territory was located posterolaterally, followed anteriorly by the associative region, and further antero-ventrally by the limbic territory. While this organizational pattern was observed across patients, there was considerable variability among patients. The organization of the functional territories of the GPi was remarkably reproducible in intra-subject scans. Furthermore, the organizational pattern was observed consistently by performing the parcellation of the GPi via the thalamus and via a different pathway, going through the striatum. Finally, the active therapeutic contact of the DBS electrode, identified with a combination of post-operative imaging and post-surgery DBS programming, overlapped with the high-probability "motor" region of the GPi as defined by imaging-based methods. The consistency, validity, and clinical relevance of our findings have the potential for improving DBS targeting, by increasing patient-specific knowledge of subregions of the GPi to be targeted or avoided, at the stage of surgical planning, and later, at the stage when stimulation is adjusted.

Postoperative rehabilitation after deep brain stimulation surgery for movement disorders

Deep brain stimulation (DBS) is a highly efficient, evidence-based therapy for a set of neurological and psychiatric conditions and especially movement disorders such as Parkinson's disease, essential tremor and dystonia. Recent developments have improved the DBS technology. However, no unequivocal algorithms for an optimized postoperative care exist so far. The aim of this review is to provide a synopsis of the current clinical practice and to propose guidelines for postoperative and rehabilitative care of patients who undergo DBS. A standardized work-up in the DBS centers adapted to each patient's clinical state and needs is important, including a meticulous evaluation of clinical improvement and residual symptoms with a definition of goals for neurorehabilitation. Efficient and complete information transfer to subsequent caregivers is essential. A coordinated therapy within a multidisciplinary team (trained in movement disorders and DBS) is needed to achieve the long-range maximal efficiency. An optimized postoperative framework might ultimately lead to more effective results of DBS.

The Anatomical Basis for Dystonia: The Motor Network Model

Background

The dystonias include a clinically and etiologically very diverse group of disorders. There are both degenerative and non-degenerative subtypes resulting from genetic or acquired causes. Traditionally, all dystonias have been viewed as disorders of the basal ganglia. However, there has been increasing appreciation for involvement of other brain regions including the cerebellum, thalamus, midbrain, and cortex. Much of the early evidence for these other brain regions has come from studies of animals, but multiple recent studies have been done with humans, in an effort to confirm or refute involvement of these other regions. The purpose of this article is to review the new evidence from animals and humans regarding the motor network model, and to address the issues important to translational neuroscience.

Methods

The English literature was reviewed for articles relating to the neuroanatomical basis for various types of dystonia in both animals and humans.

Results

There is evidence from both animals and humans that multiple brain regions play an important role in various types of dystonia. The most direct evidence for specific brain regions comes from animal studies using pharmacological, lesion, or genetic methods. In these studies, experimental manipulations of specific brain regions provide direct evidence for involvement of the basal ganglia, cerebellum, thalamus and other regions. Additional evidence also comes from human studies using neuropathological, neuroimaging, non-invasive brain stimulation, and surgical interventions. In these studies, the evidence is less conclusive, because discriminating the regions that cause dystonia from those that reflect secondary responses to abnormal movements is more challenging.

Discussion

Overall, the evidence from both animals and humans suggests that different regions may play important roles in different subtypes of dystonia. The evidence so far provides strong support for the motor network model. There are obvious challenges, but also advantages, of attempting to translate knowledge gained from animals into a more complete understanding of human dystonia and novel therapeutic strategies.

Dystonia

INTRODUCTION

Dystonia is a clinically heterogeneous group of hyperkinetic movement disorders. Recent advances have provided a better understanding of these conditions with significant clinical impact.

SOURCES OF DATA

Peer reviewed journals and reviews. PubMed.gov.

AREAS OF AGREEMENT

A recent consensus classification, including the assessment of phenomenology and identification of the dystonia syndromes, has provided a helpful tool for the clinical assessment. New forms of monogenic dystonia have been recently identified.

AREAS OF CONTROVERSY

Despite recent advances in the understanding of dystonia, treatment remains symptomatic in most patients.

GROWING POINTS

Recent advances in genetics have provided a better understanding of the potential pathogenic mechanisms involved in dystonia. Deep brain stimulation has shown to improve focal and combined forms of dystonia and its indications are constantly expanding.

AREAS TIMELY FOR DEVELOPING RESEARCH

Growing understanding of the disease mechanisms involved will allow the development of targeted and disease-modifying therapies in the future.

Non-invasive brain stimulation for dystonia: therapeutic implications

Dystonia is characterized by excessive muscle contractions giving rise to abnormal posture and involuntary twisting movements. Although dystonia syndromes are a heterogeneous group of disorders, certain pathophysiological mechanisms have been consistently identified across different forms. These pathophysiological mechanisms have subsequently been exploited for the development of non-invasive brain stimulation (NIBS) techniques able to modulate neural activity in one or more nodes of the putative network that is altered in dystonia, and the therapeutic role of NIBS has hence been suggested. Here all studies that applied such techniques as a therapeutic intervention in any forms of dystonia, including the few works performed in children, are reviewed and emerging concepts and pitfalls of NIBS are discussed.

Research Priorities in Limb and Task-Specific Dystonias

Dystonia, which causes intermittent or sustained abnormal postures and movements, can present in a focal or a generalized manner. In the limbs, focal dystonia can occur in either the upper or lower limbs and may be task-specific causing abnormal motor performance for only a specific task, such as in writer’s cramp, runner’s dystonia, or musician’s dystonia. Focal limb dystonia can be non-task-specific and may, in some circumstances, be associated with parkinsonian disorders. The true prevalence of focal limb dystonia is not known and is likely currently underestimated, leaving a knowledge gap and an opportunity for future research. The pathophysiology of focal limb dystonia shares some commonalities with other dystonias with a loss of inhibition in the central nervous system and a loss of the normal regulation of plasticity, called homeostatic plasticity. Functional imaging studies revealed abnormalities in several anatomical networks that involve the cortex, basal ganglia, and cerebellum. Further studies should focus on distinguishing cause from effect in both physiology and imaging studies to permit focus on most relevant biological correlates of dystonia. There is no specific therapy for the treatment of limb dystonia given the variability in presentation, but off-label botulinum toxin therapy is often applied to focal limb and task-specific dystonia. Various rehabilitation techniques have been applied and rehabilitation interventions may improve outcomes, but small sample size and lack of direct comparisons between methods to evaluate comparative efficacy limit conclusions. Finally, non-invasive and invasive therapeutic modalities have been explored in small studies with design limitations that do not yet clearly provide direction for larger clinical trials that could support new clinical therapies. Given these gaps in our clinical, pathophysiologic, and therapeutic knowledge, we have identified priorities for future research including: the development of diagnostic criteria for limb dystonia, more precise phenotypic characterization and innovative clinical trial design that considers clinical heterogeneity, and limited available number of participants.

Deep brain stimulation for dystonia: a novel perspective on the value of genetic testing

The dystonias are a group of disorders characterized by excessive muscle contractions leading to abnormal movements and postures. There are many different clinical manifestations and underlying causes. Deep brain stimulation (DBS) provides an effect treatment, but outcomes can vary considerably among the different subtypes of dystonia. Several variables are thought to contribute to this variation including age of onset and duration of dystonia, specific characteristics of the dystonic movements, location of stimulation and stimulator settings, and others. The potential contributions of genetic factors have received little attention. In this review, we summarize evidence that some of the variation in DBS outcomes for dystonia is due to genetic factors. The evidence suggests that more methodical genetic testing may provide useful information in the assessment of potential surgical candidates, and in advancing our understanding of the biological mechanisms that influence DBS outcomes.

Deep brain stimulation for myoclonus-dystonia syndrome with double mutations in DYT1 and DYT11

Myoclonus-dystonia syndrome (MDS) is a rare autosomal dominant inherited disorder characterized by the presentation of both myoclonic jerks and dystonia. Evidence is emerging that deep brain stimulation (DBS) may be a promising treatment for MDS. However, there are no studies reporting the effects of DBS on MDS with double mutations in DYT1 and DYT11. Two refractory MDS patients with double mutations were treated between 2011 and 2015 in our center. Genetic testing for DYT1 and DYT11 was performed through polymerase chain reaction amplification and direct sequencing of the specific exons of genes. For the first patient, initial bilateral ventral intermediate thalamus nucleus (Vim) DBS was performed. Because of worsening dystonia after initial improvement in symptoms, subsequent bilateral globus pallidus internus (GPi) DBS was offered at 43 months after initial surgery, which reversed the deterioration and restored the motor function. For the second patient, initial improvement in motor symptoms and quality of life was sustained at the follow-up 6 months after bilateral Vim DBS treatment. Thus, DBS may be an effective therapeutic option for MDS, even in patients with double mutations. Moreover, GPi DBS may be used as a supplementary treatment when initial Vim DBS fails to control MDS symptoms.

Cerebral plasticity: Windows of opportunity in the developing brain

BACKGROUND

Neuroplasticity refers to the inherently dynamic biological capacity of the central nervous system (CNS) to undergo maturation, change structurally and functionally in response to experience and to adapt following injury. This malleability is achieved by modulating subsets of genetic, molecular and cellular mechanisms that influence the dynamics of synaptic connections and neural circuitry formation culminating in gain or loss of behavior or function. Neuroplasticity in the healthy developing brain exhibits a heterochronus cortex-specific developmental profile and is heightened during "critical and sensitive periods" of pre and postnatal brain development that enable the construction and consolidation of experience-dependent structural and functional brain connections.

PURPOSE

In this review, our primary goal is to highlight the essential role of neuroplasticity in brain development, and to draw attention to the complex relationship between different levels of the developing nervous system that are subjected to plasticity in health and disease. Another goal of this review is to explore the relationship between plasticity responses of the developing brain and how they are influenced by critical and sensitive periods of brain development. Finally, we aim to motivate researchers in the pediatric neuromodulation field to build on the current knowledge of normal and abnormal neuroplasticity, especially synaptic plasticity, and their dependence on "critical or sensitive periods" of neural development to inform the design, timing and sequencing of neuromodulatory interventions in order to enhance and optimize their translational applications in childhood disorders of the brain.

METHODS

literature review.

RESULTS

We discuss in details five patterns of neuroplasticity expressed by the developing brain: 1) developmental plasticity which is further classified into normal and impaired developmental plasticity as seen in syndromic autism spectrum disorders, 2) adaptive (experience-dependent) plasticity following intense motor skill training, 3) reactive plasticity to pre and post natal CNS injury or sensory deprivation, 4) excessive plasticity (loss of homeostatic regulation) as seen in dystonia and refractory epilepsy, 6) and finally, plasticity as the brain's "Achilles tendon" which induces brain vulnerability under certain conditions such as hypoxic ischemic encephalopathy and epileptic encephalopathy syndromes. We then explore the unique feature of "time-sensitive heightened plasticity responses" in the developing brain in the in the context of neuromodulation.

CONCLUSION

The different patterns of neuroplasticity and the unique feature of heightened plasticity during critical and sensitive periods are important concepts for researchers and clinicians in the field of pediatric neurology and neurodevelopmental disabilities. These concepts need to be examined systematically in the context of pediatric neuromodulation. We propose that critical and sensitive periods of brain development in health and disease can create "windows of opportunity" for neuromodulatory interventions that are not commonly seen in adult brain and probably augment plasticity responses and improve clinical outcomes.

An unexpectedly high rate of revisions and removals in deep brain stimulation surgery: Analysis of multiple databases

INTRODUCTION

Deep brain stimulation (DBS) is an established therapy for movement disorders, and is under active investigation for other neurologic and psychiatric indications. While many studies describe outcomes and complications related to stimulation therapies, the majority of these are from large academic centers, and results may differ from those in general neurosurgical practice.

METHODS

Using data from both the Centers for Medicare and Medicaid Services (CMS) and the National Surgical Quality Improvement Program (NSQIP), we identified all DBS procedures related to primary placement, revision, or removal of intracranial electrodes. Cases of cortical stimulation and stimulation for epilepsy were excluded.

RESULTS

Over 28,000 cases of DBS electrode placement, revision, and removal were identified during the years 2004-2013. In the Medicare dataset, 15.2% and of these procedures were for intracranial electrode revision or removal, compared to 34.0% in the NSQIP dataset. In NSQIP, significant predictors of revision and removal were decreased age (odds ratio (OR) of 0.96; 95% CI: 0.94, 0.98) and higher ASA classification (OR 2.41; 95% CI: 1.22, 4.75). Up to 48.5% of revisions may have been due to improper targeting or lack of therapeutic effect.

CONCLUSION

Data from multiple North American databases suggest that intracranial neurostimulation therapies have a rate of revision and removal higher than previously reported, between 15.2 and 34.0%. While there are many limitations to registry-based studies, there is a clear need to better track and understand the true prevalence and nature of such failures as they occur in the wider surgical community.

Diagnosis and Management of Dystonia

PURPOSE OF REVIEW

This article highlights the clinical and diagnostic tools used to assess and classify dystonia and provides an overview of the treatment approach.

RECENT FINDINGS

In the past 4 years, the definition and classification of dystonia have been revised, and new genes have been identified in patients with isolated hereditary dystonia (DYT23, DYT24, and DYT25). Expanded phenotypes were reported in patients with combined dystonia, such as those with mutations in ATP1A3. Treatment offerings have expanded as there are more neurotoxins, and deep brain stimulation has been employed successfully in diverse populations of patients with dystonia.

SUMMARY

Diagnosis of dystonia rests upon a clinical assessment that requires the examiner to understand the characteristic disease features that are elicited through a careful history and physical examination. The revised classification system uses two distinct nonoverlapping axes: clinical features and etiology. A growing understanding exists of both isolated and combined dystonia as new genes are identified and our knowledge of the phenotypic presentation of previously reported genes has expanded. Genetic testing is commercially available for some of these conditions. Treatment options for dystonia include pharmacologic therapy, chemodenervation, and surgical intervention. Deep brain stimulation benefits many patients with various types of dystonia.

The Symptomatic Treatment of Acquired Dystonia: A Systematic Review

Background

Acquired dystonia is caused by an acquired or exogenous event. Although the therapeutic armamentarium used in clinical practice is more or less similar to that used for inherited or idiopathic dystonia, formal proof of the efficacy of these interventions in acquired dystonia is lacking.

Methods

The authors attempt to provide a comprehensive and systematic review of the current evidence for medical and allied health care treatment strategies in acquired dystonias. The PubMed, Cochrane Library, MEDLINE, Web of Science, PiCarta, and PsycINFO databases were searched up to December 2015, including randomized controlled trials, patient-control studies, and case series or single case reports containing a report on clinical outcome.

Results

There are level 3 practice recommendations for botulinum toxin injections and globus pallidus pars interna deep brain stimulation for tardive dystonia and dystonic cerebral palsy as well as intrathecal baclofen for dystonic cerebral palsy. There are insufficient and conflicting data on the effect (vs. the hazard) of other pharmacological interventions, and limited work has been done on other forms of neurostimulation and allied health care. Because no class A1 or A2 studies were identified, level 1 or 2 practice recommendations could not be deducted for a specific treatment intervention.

Conclusions

To improve the current medical and allied health care treatment options for patients with acquired dystonia, high-quality trials that examine the efficacy of therapies need to be performed.